The present invention relates to a gas pressure welding system.
A process of gas pressure welding is extensively applied to joining of such steel members as reinforcing steel bars and rails. In conventional practice, gas pressure welding has been conducted mainly by manual operation. In the case of the conventional practice, the workmanship of an operator constitutes a key factor to influence the quality of a joint. By the automation of the process of pressure welding, the process can be standardized, the quality of a joint can be stabilized, and improvement of the reliability of the joint can be achieved. From such a viewpoint, these inventors have already made proposals with regard to automatic gas pressure welding systems, as disclosed in Japanese Pat. No. 83,648(1974) and Japanese Pat. No. 115,050(1974). In the systems, progress of respective stages of the process is all properly controlled in conformity with a certain timetable preset in a program timer. However, in case the progress of the process is all controlled in conformity with a preset timetable as this, heating is caused to be insufficient in some case due to some external factors, for instance, reduction in flow of gas, the wind, and/or the like. As a result, set time elapses while an interstice is still devoid of being properly joined. In such a case, the interstice thus remaining unjoined between steel members is caused to be subjected to oxidation, thus resulting in defective joining. Besides, to cope with bulge (increase in the diameter) of a joint to be produced by heating and pressing, especially in the case of a reinforcing bar or the like that is put to use in as-weld state after being subjected to pressure welding, the diameter of the bulged joint is required to have a proper size, for instance, 14D-16D, when the diameter of the reinforcing steel bar is taken as D. However, the degree of expansion is influenced by the temperature of a heated section, distribution of the temperature, and the like. Therefore, in the case of control by preset time alone, the reinforcing steel bar is influenced by external factors, thus resulting in that pressing either falls short or is excessive in some case.